Upthrust Module for Well Fluid Pump

ABSTRACT

A well fluid pump assembly includes a rotary pump having a rotatable pump shaft. A motor is cooperatively engaged with the pump shaft for rotating the pump shaft. An upthrust module has an upthrust module housing having a lower end secured by a threaded engagement to an upper end of the pump. An upthrust module shaft is rotatably mounted in the housing and has a lower end in engagement with an upper end of the pump shaft for transferring upthrust on the pump shaft to the upthrust module shaft. An upthrust base is stationarily mounted in the housing. An upthrust runner is mounted to the upthrust module shaft for rotation therewith and located below the upthrust base. The upthrust runner engages the upthrust base to transfer to the housing upthrust applied to the upthrust module shaft from the pump shaft.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to provisional application Ser. No. 61/897,031 filed Oct. 29, 2013.

FIELD OF THE DISCLOSURE

This disclosure relates in general to rotary pumps for pumping well fluid and in particular to an upthrust module that can be bolted to an upper end of the pump for severe upthrust conditions.

BACKGROUND OF THE DISCLOSURE

Electrical submersible pumps (ESP) are often employed to pump well fluid from wells. A typical ESP includes a rotary pump driven by an electrical motor. Normally, the ESP is suspended in the well on a string of production tubing. A seal section, usually located between the motor and the pump, has a movable element to reduce a pressure differential between the well fluid exterior of the motor and motor lubricant contained in the motor. The pump may be a centrifugal pump having a plurality of stages, each stage having an impeller and a diffuser. The pump alternately may be another type.

During operation both downthrust and upthrust may occur. During downthrust, a force is imposed on the pump shaft tending to push the pump shaft downward, or upstream. During upthrust, a force is imposed on the pump shaft tending to push the pump shaft upward or downstream. Centrifugal pumps have thrust bearings associated with at least some, and sometimes all of the stages. The pump stage thrust bearings may transfer both upthrust and downthrust to the diffusers and to the pump housing.

Also, a separate thrust bearing unit will normally be located below the pump. The thrust bearing components in the thrust bearing unit are immersed in motor lubricant and may be located in a lower part of the seal section. The shaft running through the thrust bearing unit will experience downthrust imposed on the pump shaft and will transfer that downthrust to the housing containing the thrust bearing unit. In some cases, the shaft running through the thrust bearing unit will also experience upthrust from the pump shaft thrust bearing unit and will transfer the upthrust to the housing containing the thrust bearing unit. Even if thrust bearings as described are contained in the pump assembly, under high upthrust conditions, the transfer of upthrust can be damaging to the pump.

SUMMARY

The well fluid pump assembly of this disclosure includes a rotary pump having a rotatable pump shaft. A motor is cooperatively engaged with the pump shaft for rotating the pump shaft. An upthrust module has an upthrust module housing with a lower end secured by a threaded engagement to an upper end of the pump. An upthrust module shaft is rotatably mounted in the housing and has a lower end in engagement with an upper end of the pump shaft for transferring upthrust on the pump shaft to the upthrust module shaft. An upthrust base is stationarily mounted in the housing. An upthrust runner is mounted to the upthrust module shaft for rotation therewith and located below the upthrust base. During upthrust, the upthrust runner engages the upthrust base to transfer to the housing upthrust applied to the upthrust module shaft from the pump shaft.

A well fluid discharge adapter may be located on an upper end of the upthrust module for connection to a sting of production tubing. A well fluid flow passage extends through the upthrust module for flowing well fluid from the pump through the upthrust module and to the production string. Preferably, the upthrust runner and the upthrust base are positioned in the housing for immersion in the well fluid flowing through the housing.

The upthrust module preferably has upper and lower radial support bearings mounted around the upthrust module shaft in the housing. The upper radial support bearing is located above the thrust runner and the upthrust base, and the lower radial support bearing is located below the thrust runner and the upthrust base. The upper and lower radial support bearings have well fluid flow passages. The upthrust base may be mounted to a lower side of the radial support bearing.

The upthrust module shaft is free to move axially a limited extent relative to the housing so as to move upward when pushed by the pump shaft during upthrust. The upper end of the pump shaft and the lower end of the upthrust module shaft are splined. A coupling sleeve with internal splines couples the upper end of the pump shaft and the lower end of the upthrust module shaft to each other for rotation therewith. The upper end of the pump shaft moves upward and abuts the lower end of the upthrust module shaft during upthrust of sufficient magnitude.

A lower thrust hearing is located below the pump and in cooperative engagement with the pump shaft for accommodating downthrust imposed on the pump shaft. The lower thrust bearing may be located in the seal section and is immersed in lubricant and sealed from the well fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features, advantages and objects of the disclosure, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the disclosure briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the disclosure and is therefore not to be considered limiting of its scope as the disclosure may admit to other equally effective embodiments.

FIG. 1 is a side view of an electrical submersible pump assembly in accordance with this disclosure.

FIG. 2 is a sectional view of the upthrust module of the pump assembly of FIG. 1.

FIGS. 3A and 3B comprise a sectional view of the seal section of the pump assembly of FIG. 1.

DETAILED DESCRIPTION OF THE DISCLOSURE

The methods and systems of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The methods and systems of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.

It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.

Referring to FIG. 1, electrical submersible pump assembly (ESP) 13 is illustrated as being located within a cased well 11. ESP 13 includes several modules, one of which is a pump 15 that may be a centrifugal pump having a large number of stages, each stage being an impeller and a diffuser. Alternately, pump 15 could be other types that undergo downthrust and upthrust. Pump 15 has an intake 17 for drawing in well fluid. Another module comprises an electrical motor 19, which drives pump 15 and is normally a three-phase AC motor. A third module comprises a protective member or seal section 21 coupled to motor 19. Seal section 21 has components to reduce a pressure differential between dielectric lubricant or oil contained in motor 19 and the pressure of the well fluid on the exterior of ESP 13. In this example, seal section 21 is located above motor 19 and below intake 17. Intake 17 may be located in an upper portion of seal section 21 or on a lower end of pump 15.

ESP 13 may also include other modules, such as a gas separator for separating gas from the well fluid prior to the well fluid flowing into pump 15. If so, intake 17 would be at a lower end of the gas separator.

In this disclosure, ESP 13 has an upthrust module 23 mounted to the upper end of pump 15. The various modules may be shipped to a well site apart from each other, then assembled with bolts or other types of fasteners. Upthrust module 23 has an production tubing adapter 25 on its upper end that secures to a string of production tubing 27. A power cable 29 extends from motor 19 alongside tubing 27 to a wellhead for supplying power to motor 19.

Although shown in cased well 11, ESP 13 can alternately be located on the surface adjacent a wellhead. In that instance, ESP 13 would boost the pressure of well fluid flowing to it such as for injecting the fluid into a well. If on the surface, ESP 13 would likely be horizontal rather than vertical as shown in the drawings. If located on the surface, seal section 21 would not be required. Although cased well 11 is shown as a vertical well, it could have an inclined or horizontal section in which ESP 11 locates. The terms “upper”, “lower”, “upthrust”, and “downthrust” are used herein only for convenience and not in a limiting manner.

FIG. 2 illustrates one example of the components of upthrust module 23. A tubular base 31 is at the lower end of upthrust module 23. Base 31 may connect by a threaded engagement to the upper end of pump 15 in a variety of manners. FIG. 2 illustrates an external flange 33 on base 31 through which bolts 35 extend into threaded holes in pump discharge end 37.

A lower radial support hearing 39 is stationarily mounted in base 31. Lower radial bearing 39 has a central opening or journal that is in sliding engagement with a lower shaft sleeve 41. Lower shaft sleeve 41 is secured to an upthrust module shaft 43 for rotation therewith. Lower radial bearing 39 has flow passages 45 extending axially through. It for the passage of well fluid, as indicated by the arrows. Upthrust module shaft 43 has a splined lower end 46 that is approximately flush with the lower end of upthrust module base 31.

A cylindrical housing 47 secures by internal threads to external threads on the upper end of base 31. An internal, cylindrical spacer 49 is closely received, in the inner diameter of housing 47 and has a lower end in abutment with an upper end of lower radial bearing 39. An upper radial support bearing 51 is located in the inner diameter of housing 47 and has a lower end in abutment with spacer 49. Upper radial bearing 51 has a central opening or journal that slidingly receives an upper shaft sleeve 53 keyed to shaft 43 for rotation therewith. Upper radial bearing 51 also has axial flow passages 55 for the passage of well fluid. Upper and lower retaining rings 57, 58 retain shaft 43 within upper and lower radial bearings 51, 39. Upper retaining ring 57 is located, above upper radial bearing 51 and lower retaining ring 58 below lower radial bearing 39. The distance between upper and lower retaining rings 57, 58 is greater than the distance from the lower side of lower radial bearing 39 to the upper side of upper radial bearing 51 to as to allow some axial play of shaft 43 relative to upper and lower radial bearings 51, 39 and to housing 47. The upper end of shaft 43 terminates within housing 47 a short distance above upper radial bearing 51.

An upthrust runner 59 is mounted to shaft 43 between lower radial bearing 39 and upper radial bearing 51. A retaining ring 61 supports upthrust runner 59 axially on shaft 43, and a key (not shown) causes upthrust runner 59 to rotate in unison with shaft 43. Upthrust runner 59 has an upper surface that will slidingly engage a thrust base or pads 63 secured to the lower side of upper radial bearing 51 during upthrust. Alternately, thrust pads could be mounted to upthrust runner 59. The engagement of runner 59 with thrust base 63 occurs during upthrust conditions on shaft 43. The outer diameters of thrust runner 59 and thrust base 63 are much smaller than the inner diameter of housing 47, creating an annular clearance for the flow of well fluid.

A discharge head 67 with an upward converging bore 68 has external threads that engage internal threads in housing 47 above upper radial bearing 51. The lower end of discharge head 67 bears against the upper side of upper radial bearing 51, stationarily securing upper radial bearing 51 in housing 47. The downward force of the threaded engagement of discharge head 67 transfers through upper radial bearing 51 and spacer 49 to lower radial bearing 39 to tightly secure both upper and lower radial bearings 51, 39 in housing 47. Discharge head 67 secures by a threaded engagement to production tubing adapter 25. In this example, bolts 69 extend through holes in production tubing adapter 25 into threaded holes in discharge head 67.

The lower end of upthrust module shaft 43 has axially extending splines that mesh with internal splines in a splined coupling 70. The upper end of a pump shaft 71 is also splined and in meshing engagement with the internal splines in splined coupling 70. The upper end of pump shaft 71 is in contact with the lower end of upthrust module shaft 43 when upthrust occurs on pump shaft 71. When downthrust occurs on pump shaft 71, a small clearance between upthrust module shaft 43 and pump shaft 71 may exist, unless pump shaft 71 and thrust module shaft 43 are fixed to each other for axial movement in both upthrust and downthrust conditions.

In this embodiment, upthrust module 23 transfers only upthrust on pump shaft 71 to housing 47 and not downthrust. ESP 13 has a lower thrust bearing unit assembly that handles downthrust on pump shaft 73. The thrust bearing assembly could be in a lower portion of seal section 21, an upper portion of motor 19, or in a separate module coupled between seal section 21 and motor 19 (FIG. 1). FIGS. 3A and 3B provide an example of a thrust bearing assembly located within the lower portion of seal section 21. A variety of thrust bearing assemblies other than the one shown are also feasible.

Seal section 21 has an axially extending shaft 72 that transmits rotation from a motor shaft (not shown) to pump shaft 71 (FIG. 2). A flexible bag or bellows 73 is normally located, in a seal section housing 75. Well fluid is admitted to housing 75 on the exterior of bag 73, and lubricant from motor 19 is in fluid communication with the interior of bag 73. A lower chamber 77 filled with motor lubricant may be within housing 75 below bag 73.

The lower thrust bearing assembly includes a runner 79 rigidly mounted to seal section shaft 72 and which has a lower side located above a stationary downthrust base 81 mounted in seal section housing 75. Downthrust base 81 is supported on a lower adapter 83 of seal section 21. Lower adapter 83 bolts to the upper end of motor 19 (FIG. 1). Downthrust imposed on pump shaft 71 (FIG. 2) transfers to seal section shaft 72, and from there through downthrust runner 79 to downthrust base 81.

It is not necessary for the thrust bearing assembly in seal section 21 to handle upthrust, but optionally it may. Unless the lower end of pump shaft 71 is secured or latched axially to the upper end of seal section shaft 72, any upthrust imposed on pump shaft 71 by the pump stages will not transfer to seal section shaft 72. Consequently, the thrust bearing assembly in seal section 21 may be configured to handle only downthrust.

It is known to axially latch a pump shaft to a seal section shaft to transfer upthrust to a thrust bearing assembly below the pump. Also, it is known to configure a thrust bearing assembly below the pump so as to transfer both upthrust and downthrust. The thrust bearing assembly shown in FIG. 3B optionally has features to transfer both downthrust and upthrust. This arrangement allows the operator to employ ESP 13 without upthrust module 23 for conditions in which the upthrust is not expected to be severe enough to merit upthrust module 23. In FIG. 3B, the thrust bearing assembly in seal section 21 has an upthrust base 85 mounted above thrust runner 79. Upthrust base 85 is stationarily mounted in seal section housing 75, such as by a retaining ring 87. During upthrust conditions, thrust runner 79 engages and transfers upthrust to upthrust base 85 if seal section shaft 72 is latched axially to pump shaft 71. At the same time, if upthrust module 23 is employed, it too will receive and absorb upthrust from pump shaft 71.

Thrust runner 79, downthrust base 81 and upthrust base 85 are located in a portion of seal section housing 75 that contains motor lubricant in fluid communication with the motor lubricant in motor 19 (FIG. 1). Thus thrust runner 79, downthrust base 81 and upthrust base 85 are immersed in the motor lubricant. The lubricant is sealed from well fluid on the exterior of seal section 21.

Each impeller (not shown) within pump 15 will transmit upthrust to the next upper diffuser because the impellers are normally allowed to float axially a limited amount on pump shaft 71. The transfer of some of the upthrust from impellers to diffusers may occur whether or not upthrust module 23 is utilized. Thus, if the upthrust is not expected to be high, an operator may chose to not use upthrust module 23. However, in extreme conditions, excessive damage to the pump stages can occur unless upthrust module 23 is employed.

While the disclosure has been shown in only one of its forms, it should be apparently to those skilled in the art that it is susceptible to various modifications. 

1. A well fluid pump assembly, comprising: a rotary pump having a rotatable pump shaft; a motor cooperatively engaged with the pump shaft for rotating the pump shaft; an upthrust module, comprising: an upthrust module housing having a lower end secured by a threaded engagement to an upper end of the pump; an upthrust module shaft rotatably mounted in the housing and having a lower end in engagement with an upper end of the pump shaft for transferring upthrust on the pump shaft to the upthrust module shaft; an upthrust base stationarily mounted in the housing; and an upthrust runner mounted to the upthrust module shaft for rotation therewith and located below the upthrust base, the upthrust runner engaging the upthrust base to transfer to the housing upthrust applied to the upthrust module shall from the pump shaft.
 2. The assembly according to claim 1, further comprising: a well fluid discharge adapter on an upper end of the upthrust module for connection to a string of production tubing.
 3. The assembly according to claim 1, further comprising: a well fluid flow passage extending through the upthrust module for flowing well from the pump through the upthrust module and to a wellhead.
 4. The assembly according to claim 1, further comprising: a well fluid flow passage extending through the housing for flowing well fluid from the pump through the upthrust module; and wherein the upthrust runner and the upthrust base are positioned in the housing for immersion in the well fluid flowing through the upthrust module.
 5. The assembly according to claim 1, further comprising: upper and lower radial support hearings mounted around the upthrust module shaft in the housing; the upper radial support bearing being located above the thrust runner and the upthrust base; and the lower radial support bearing located below the thrust runner and the upthrust base.
 6. The assembly according to claim 1, wherein the upthrust module shaft is free to move axially a limited extent relative to the housing.
 7. The assembly according to claim 1, wherein: the upper end of the pump shaft and the lower end of the upthrust module shaft are splined; and a coupling sleeve with internal splines couples the upper end of the pump shaft and the lower end of the upthrust module shaft to each other for rotation therewith.
 8. The assembly according to claim 1, further comprising: a radial support bearing mounted in the housing through which the upthrust module shaft extends; and wherein the upthrust base is mounted to a lower side of the radial support bearing.
 9. The assembly according to claim 1, further comprising: a below pump thrust bearing located below the pump and in cooperative engagement with the pump shaft for accommodating downthrust imposed on the pump shaft.
 10. The assembly according to claim 1, further comprising: a seal section mounted above the motor and below the pump, the seal section having a seal section housing containing a movable element to reduce a pressure differential between well fluid exterior of the motor and motor lubricant in the motor; a seal section shaft rotatably mounted in the seal section housing, the seal section shaft having an upper end in engagement with a lower end of the pump shaft; and a below-pump thrust bearing located in the seal section housing in engagement with the seal section shaft for accommodating downthrust imposed on the pump shaft, the below-pump thrust bearing being immersed in motor lubricant contained in the seal section housing.
 11. A submersible well pump assembly, comprising: a rotary pump having a rotatable pump shaft, the pump having a discharge on an upper end for pumping well fluid up a well; a motor located below the pump and cooperatively engaged with the pump shaft for rotating the pump shaft; a lower thrust bearing mounted below the pump and in cooperative engagement with the pump shaft for absorbing downthrust applied to the pump shaft, the lower thrust bearing being immersed in a lubricant that is sealed from well fluid in the well; and an upper thrust bearing mounted to the discharge of the pump such that the upper thrust bearing is immersed in well fluid pumped by the pump out the discharge, the upper thrust bearing being in cooperative engagement with the pump shaft for absorbing upthrust on the pump shaft.
 12. The assembly according to claim 11, wherein the upper thrust bearing comprises: an upthrust module housing having a lower end secured by a threaded engagement to the discharge of the pump; an upthrust module shaft rotatably mounted in the housing and having a lower end in engagement with an upper end of the pump shaft for transferring upthrust on the pump shaft to the upthrust module shaft; an upthrust base stationarily mounted in the housing; and an upthrust runner mounted to the upthrust module shaft for rotation therewith and located below the upthrust base, the upthrust runner being axially movable with the upthrust module shaft and rotatably engaging the upthrust base to transfer to the housing upthrust applied to the upthrust module shaft from the pump shaft.
 13. The assembly according to claim 12, further comprising: a well fluid discharge adapter on an upper end of the upthrust module for connection to a string of production tubing.
 14. The assembly according to claim 12, further comprising: upper and lower radial support hearings mounted around the upthrust module shaft in the housing; the upper radial support bearing being located above the thrust runner and the upthrust base, and the lower radial support bearing located below the thrust runner and the upthrust base; and each of the upper and lower radial support bearings having a well fluid flow passage for flowing well fluid from the discharge of the pump through the housing.
 15. The assembly according to claim 12, further comprising: upper and lower radial support bearings mounted around the upthrust module shaft in the housing; the upthrust base being mounted to a lower side of the upper radial support bearing; the upper and lower radial support bearings each having a well fluid flow passage; and wherein annular clearances surround the upthrust base and upthrust runner within the housing flowing well fluid from the discharge of the pump through the housing.
 16. The assembly according to claim 12, wherein the upthrust module shaft is free to move axially a limited extent relative to the housing.
 17. A method of pumping well fluid, comprising: (a) cooperatively coupling a motor to a rotary pump having a rotatable pump shaft and a discharge end; (b) providing an upthrust module with an upthrust module housing, an upthrust module shaft rotatably mounted in the housing, an upthrust base stationarily mounted in the housing, and an upthrust runner mounted to the upthrust module shaft for rotation therewith; (c) securing the upthrust module housing to the discharge end of the pump and coupling the upthrust module shaft to the pump shaft; (d) operating the pump to pump well fluid out the discharge end and through the upthrust module housing; and (e) during upthrust of sufficient magnitude, pushing the upthrust module shaft upward with the pump shaft, causing the upthrust runner to engage the upthrust base and transfer upthrust imposed on the upthrust module shaft to the upthrust runner.
 18. The method according to claim 17, wherein: step (d) comprises immersing the upthrust base and the upthrust runner in the well fluid flowing through the upthrust module housing.
 19. The method according to claim 17, further comprising: in step (a), mounting a downthrust bearing between the motor and the pump; and during downthrust, transferring downthrust imposed on the pump shaft to the downthrust bearing.
 20. The method according to claim 17, wherein: step (d) comprises lowering the motor and the pump into well fluid within a well; step (d) further comprises immersing the upthrust base and the upthrust runner in the well fluid flowing through the upthrust module housing; and wherein the method further comprises: in step (a), mounting a downthrust bearing within a lubricated environment between the motor and the pump that is sealed from the well fluid; and during downthrust, transferring downthrust imposed on the pump shaft to the downthrust bearing. 